A double surfaces sliding mode control technique in rotary drilling system

In this paper, a conventional model describing the torsional behavior of a generic vertical oilwell drillstring has been presented, and a PI control based on sliding mode is proposed for robust stabilization of nonlinear rotary drilling system. The controller is combined of a PI controller to compensate the nonlinearity in the drilling machine and sliding mode controller to ensure the robustness of the method proposed. A double sliding mode surfaces control is applied in the control system. The control target is to give rise to bit stick-slip oscillations and bit sticking phenomena, to accomplish the bit velocity to the rotary velocity and the rotary velocity approach to the reference. The simulation results show faster dynamics performance, and a strong potential for the practical applicability of this approach.